package 牛客网_N.查找_递归_排序_贪心.统计每个月兔子的总数;

import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		System.out.println(getTotalCount(n));
	}

	public static int getTotalCount(int n) {
		int[] dp = new int[n+1];
		dp[0] = 0;
		dp[1] = 1;
		for(int i = 2; i < n+1; i++){
			dp[i] = dp[i-1] +dp[i-2]; 
		}
		return dp[n];
	}
}
